This invention is directed to a gasket for a manway opening for containment vessels such as railroad cars, particularly tank cars. More particularly it is directed to a manway gasket with enhanced sealing capability and with visual recognition capability for verification of its presence.
A manway or hatch provides access to the interior of a containment vessel such as a railroad tank car for loading, venting, cleaning and maintenance. During transit the manway opening is closed by a cover. The cover is normally hinged and latched to the loading nozzle which is the upstanding tube surrounding the opening in the car body. The nozzle may be a cylindrical tube, or it may have a rounded top edge known as a coaming.
The cover is normally attached to the car by a hinge element. It is held in place by a series of six or eight bolts equally spaced about the opening. A resilient gasket is provided between the cover and the upper edge of the nozzle or coaming to seal between planar annular surfaces on the top of the nozzle or coaming and the underside of the cover. One such gasket, normally affixed to the coaming or nozzle, is disclosed in U.S. Pat. No. 5,678,827. The design is available commercially from Salco Products, Inc., Lemont, Ill.
An adequate seal between the cover and manway opening structure is an important aspect of gasket function. It is particularly difficult to achieve because of the generally rough treatment of the edge of the coaming or nozzle during normal car usage.
In one form, the gasket includes upstanding concentric annular ribs or chevrons which contact the planar annular gasket contact surface on the under surface of the cover. These ribs, molded into the gasket about its upper sealing surface enhance the ability of the gasket to provide a fluid tight seal.
The manway cover urges the gasket against the upper edge of the coaming or nozzle. It is drawn toward closure by six or eight or more bolts equally spaced about the outer perimeter of the manway opening. Necessarily, the clamping force imparted to the gasket member by the coacting annular gasket contact surfaces on the cover an associated nozzle or coaming is maximized nearest the bolt locations. It further follows that the minimum clamping force is imparted at a location midway between bolts.
The presence of a resilient gasket element between the manway nozzle and cover is important in the operation and usage of railroad cars having manway openings. Particularly important is the capability to verify its presence from the ground level adjacent to the cars. This is a safety feature not only from the standpoint of assuring the integrity of the seal, but from the standpoint of eliminating the need for personnel to climb to the upper heights of the railroad equipment to perform manual verification.